# TDP43 Q331K Research Report **Protein:** TDP43 Q331K **Variant:** Q331K **UniProt ID:** Q13148 **Disease Association:** ALS / FTD **Report Generated:** 2026-07-28 19:24 UTC **AlphaFold Confidence (pLDDT):** 64.6% **Structure Folded:** 2026-06-20 --- ## Structure Summary TDP-43 is a protein that normally helps regulate RNA in cells, but when it malfunctions it causes ALS and frontotemporal dementia (FTD) by forming toxic clumps in nerve cells. This analysis examined the Q331K variant using computer modeling, producing a structure with moderate-to-low average confidence (64.6 pLDDT), suggesting significant uncertainty in the predicted structure. The low confidence limits concrete structural insights, though the variant sits in a region known to be important for TDP-43's disease-related behavior. --- TDP-43 (TAR DNA-binding protein 43) is an RNA-binding protein essential for RNA metabolism, normally functioning in the cell nucleus. In ALS and FTD, TDP-43 misfolds and accumulates in toxic aggregates outside the nucleus, a pathological hallmark found in over 97% of ALS cases and nearly half of FTD cases [3]. The Q331K variant involves a change from glutamine to lysine at position 331, located in TDP-43's intrinsically disordered C-terminal domain (CTD), a region critical for both normal condensate formation and pathological aggregation [2][4]. The structural prediction for Q331K was generated using AlphaFold2/ColabFold methodology, yielding an average confidence score (pLDDT) of 64.6. This moderate-to-low confidence indicates substantial uncertainty in the predicted structure, particularly expected for the CTD region which is intrinsically disordered and lacks a stable folded structure [4]. Confidence scores below 70 indicate that specific structural details should be interpreted with considerable caution, as the model cannot reliably predict the conformation of disordered regions. The CTD's flexible nature is functionally important—it enables TDP-43 to undergo phase transitions into liquid-like condensates such as stress granules, but mutations in this region can drive aberrant transitions into solid, amyloid-like aggregates [2][4]. The Q331K substitution replaces a polar, uncharged glutamine with a positively charged lysine, potentially altering the electrostatic properties and phase behavior of the CTD. Research has shown that mutations in TDP-43's C-terminal alpha-helix region can uncouple normal condensate formation from pathological amyloid assembly [4], suggesting that charge changes like Q331K might similarly disrupt the protein's phase transition dynamics. Additionally, studies demonstrate that TDP-43 pathology involves complex molecular crosstalk with other proteins and is modulated by cellular factors that regulate phase behavior and nuclear-cytoplasmic transport [1][2], providing context for how single amino acid changes might trigger disease cascades. Given the low structural confidence and the inherently disordered nature of this protein region, the primary research value lies in recognizing Q331K as a variant in a functionally critical domain rather than in specific atomic-level structural predictions. The charge alteration from Q to K at position 331 occurs in a region where TDP-43's conformational dynamics directly influence its aggregation propensity and neurotoxic activity [2][4]. Understanding such variants contributes to the broader effort to identify biomarkers and therapeutic targets for ALS and FTD, conditions where distinguishing between TDP-43 and tau pathology is clinically important for guiding treatment strategies [3]. ## Works Cited [1] Ribeiro et al. (2026). Molecular Modulation of the Crosstalk Between TDP-43 and SOD1. International journal of molecular sciences. [PubMed](https://pubmed.ncbi.nlm.nih.gov/42074053/) [2] Chin et al. (2026). Nuclear export modulates TDP-43 phase transition and cytoplasmic aggregation. bioRxiv : the preprint server for biology. [PubMed](https://pubmed.ncbi.nlm.nih.gov/41993496/) [3] Honey et al. (2026). An acetylated Tau-174 CSF biomarker discriminates between TDP-43 and tau pathology in patients with frontotemporal lobar degeneration. Nature medicine. [PubMed](https://pubmed.ncbi.nlm.nih.gov/41986736/) [4] Byrd et al. (2026). An ALS-associated mutation in the C-terminal alpha-helix of TDP-43 uncouples condensate formation and amyloid assembly. Protein science : a publication of the Protein Society. [PubMed](https://pubmed.ncbi.nlm.nih.gov/41969219/) ## Similar Research **Integrative genetic analysis illuminates ALS heritability and identifies risk genes.** Megat et al. (2023) *Related research* [Read on PubMed](https://pubmed.ncbi.nlm.nih.gov/36670122/) **Biomarker discovery in Alzheimer's and neurodegenerative diseases using Nucleic Acid Linked Immuno-Sandwich Assay.** Ashton et al. (2025) *Related research* [Read on PubMed](https://pubmed.ncbi.nlm.nih.gov/40401628/) **Frontotemporal dementia. How to deal with its diagnostic complexity?** Antonioni et al. (2025) *Related research* [Read on PubMed](https://pubmed.ncbi.nlm.nih.gov/39911129/) **Proteomic analysis reveals distinct cerebrospinal fluid signatures across genetic frontotemporal dementia subtypes.** Sogorb-Esteve et al. (2025) *Related research* [Read on PubMed](https://pubmed.ncbi.nlm.nih.gov/39908349/) **MATR3 pathogenic variants differentially impair its cryptic splicing repression function.** Khan et al. (2024) *Related research* [Read on PubMed](https://pubmed.ncbi.nlm.nih.gov/38320753/) --- ## Open Targets Disease Associations | Disease | Score | Data Sources | |---------|-------|--------------| | amyotrophic lateral sclerosis | 0.820 | literature, animal_model, genetic_association, genetic_literature | | frontotemporal dementia with motor neuron disease | 0.707 | literature, animal_model, genetic_association, genetic_literature | | familial amyotrophic lateral sclerosis | 0.480 | literature, animal_model, genetic_literature | | frontotemporal dementia | 0.453 | literature, animal_model, genetic_association, genetic_literature | | neurodegenerative disease | 0.453 | literature, affected_pathway | | motor neuron disorder | 0.446 | literature, genetic_association | | amyotrophic lateral sclerosis, dominant | 0.370 | genetic_literature | | hereditary disease | 0.191 | literature, genetic_association | | immunodeficiency due to MASP-2 deficiency | 0.188 | genetic_association | | Parkinson disease | 0.147 | literature, animal_model, genetic_association | *...and 2568 more associations* --- ## AI Research Brief # Research Brief: TDP-43 Q331K Variant ## Pathogenic Mechanisms The TDP-43 Q331K variant represents a substitution in a protein critical for RNA metabolism and cellular homeostasis. TDP-43 functions through DNA binding and double-stranded DNA binding activities, while regulating mRNA stability through both 3'-UTR-mediated stabilization and destabilization mechanisms. The Q331K mutation introduces a charge reversal (glutamine to lysine) that may disrupt the protein's normal interaction networks, including associations with key partners such as PPP1R15A, FUS, OTUB1, ELAVL1, and GNB2. Critically, wild-type TDP-43 is prone to amyloid fibril formation, a hallmark of neurodegenerative proteinopathies. The Q331 residue is located outside the primary aggregation hotspot (residues 228-232, aggregation score: 0.71), yet the charge alteration at position 331 could potentially influence protein stability, alter electrostatic interactions critical for normal nuclear-cytoplasmic shuttling, or modify RNA binding specificity. The variant may enhance or stabilize pathological conformations through altered protein-protein interactions or disrupted autoinhibitory mechanisms. ## Clinical Significance Currently, variant-specific clinical and pathogenicity data for Q331K are notably absent from available databases and literature. This represents a significant knowledge gap, as the clinical classification (pathogenic, likely pathogenic, or variant of uncertain significance) remains undetermined. Population frequency data are not available, preventing assessment of whether this represents a rare disease-causing mutation or a more common polymorphism. The functional consequences of the glutamine-to-lysine substitution likely involve alterations in protein charge distribution and potential disruption of normal TDP-43 localization or regulatory mechanisms, though experimental validation is critically needed. ## Therapeutic Landscape The therapeutic landscape for TDP-43 proteinopathies centers on preventing pathological aggregation. The primary aggregation hotspot spans residues 228-232, representing a potential target for intervention strategies. However, no peptide inhibitors or small molecules specifically targeting TDP-43 Q331K have been documented in the current literature. The variant's position outside the main aggregation hotspot suggests that therapeutic approaches might need to focus on stabilizing native conformations or preventing early oligomerization events rather than directly blocking fibril formation. Computational approaches to generate candidate peptides targeting the Q331K-specific altered electrostatics could represent a novel --- ## Agent Findings ### Literature (1) - **2026-06-21:** None of the analyzed papers directly investigate the TDP43 Q331K variant. The papers focus on C9orf72-related ALS/FTD, CHCHD10 mutations, general TDP-43 pathology mechanisms, protein quality control systems, and therapeutic approaches, but do not address the specific Q331K missense mutation in TARDBP/TDP43. ### Clinical (1) - **2026-06-21:** ### Structural (1) - **2026-06-21:** AlphaFold structure update: Baseline check: 2 structure(s) found ### Synthesis (1) - **2026-06-21:** Synthesis of 2 findings (peptides, supplements): The TDP-43 Q331K variant landscape reveals a nascent but developing therapeutic pipeline with limite... --- *Generated by [Clarity Protocol](https://clarityprotocol.io)* **Data Sources:** - Structure predictions: AlphaFold via ColabFold - Clinical variant data: ClinVar, gnomAD - Disease associations: Open Targets Platform - Research findings: AI agents (PubMed, clinical databases)